Health Consequences of Obesity
The relationship of body weight to mortality is also affected by age. The body weights associated with the lowest mortality increase with age, and newer weight tables take this into account. In addition, as age increases to over 65, the relationship of body weight and mortality takes on a more striking U-shape. This suggests that although obesity remains an important risk factor in the elderly, under nutrition is also extremely important.
The increase in total mortality related to obesity results predominantly from coronary heart disease (CHD). Evidence is mixed whether obesity is an independent risk factor for coronary heart disease. For example the 1993 cholesterol treatment guidelines omit obesity as a risk factor for CHD, while the previous edition in 1988 included obesity. Nonetheless, obesity is clearly an important risk factor for the development of many other CHID risk factors.
Obese individuals age 20-44, for example, have a 3.8 times greater risk of type II diabetes, 5.6 times greater risk of hypertension, and 2.1 times greater risk of hypercholesterolemia. As a result, type II diabetes and stroke also contribute to the increase in obesity-related mortality. The obese also have an increase risk of certain cancers including colon, rectum, and prostate in men and uterus, biliary tract, breast, and ovary in women.
As a result of these conditions, relative weights of 130% are associated with an excess mortality of 35%. Relative weights of 150% have a greater than two-fold excess death rate. Patients with “morbid” obesity (relative weights greater than 200%), have a greater than 10-fold increase in death rates.
Obesity is also associated with a variety of other medical disorders including degenerative joint disease of both weight bearing and non-weight bearing joints, diseases of the digestive tract (gallstones, reflux esophagitis), thromboembolic disorders, heart failure (both systolic and diastolic), respiratory impairment, and skin disorders . Obese patients also have a greater incidence of surgical and obstetric complications and are more prone to accidents. Although obesity is not associated with an increased risk of major psychiatric disorders, obese patients are at increased risk of psychological disorders and social discrimination.
Regional fat distribution:
Recent investigations suggest that the location of the excess body fat (regional fat distribution) is a major determinant of the degree of excess morbidity and mortality due to obesity. At least three components of body fat are associated with obesity-related adverse health outcomes. These are the total amount of body fat (expressed as a percentage of body weight), the amount of subcutaneous truncal or abdominal fat (upper body fat), and the amount of visceral fat located in the abdominal cavity.
These three are partly correlated with each other but exhibit a fairly high degree of independence. Each of these components of body fat is associated with varying degrees of metabolic abnormalities and independently predict adverse health outcomes. In each of 6 prospective epidemiologic studies, increased abdominal obesity was associated with increased cardiovascular and total mortality.
Body fat distribution can be assessed by a number of measurement techniques. Measurements of skin folds (sub scapular and triceps) reflect subcutaneous fat. Measurement of circumferences (waist and hip) reflects both abdominal and visceral fat. CT and MR scan measure subcutaneous and visceral fat. Clinically, measurement of the waist and hip circumference is most useful. The waist is measured at the umbilicus and the hips at the greater trochanter. A waist to hip ratio of 1.0 and 0.8 are considered normal in men and women, respectively. Ratios above these values reflect abdominal and/or visceral obesity and a greater risk of obesity-related disorders.
